Conventional electromagnet structures having a U-shaped core, a coil wound around one leg of the core, and a spring biased armature attached to the other leg of the core are used for numerous switching applications. Electromagnet relay contacts are usually attached to the armature and the core so that normally open contacts meet when coil is energized. Relays using this type of electromagnet encounter several disadvantages relating to shortcomings in the electromagnet.
In conventional electromagnets, the armature must rotate eight to ten degrees while the flux dispersion approaches 40-50% of the total generated flux. To operate the electromagnet, a relatively large amount of magnetomotive force (MMF) is needed to generate enough flux to compensate for the high degree of flux dispersion.
A large quantity of copper winding is required to produce a coil having the required MMF and for compensating for the high amount of flux dispersion. In addition, a relatively large amount of iron is required to produce the core, resulting in a bulky, slow-responding electromagnet. Conventional electromagnets encounter problems as a result of hard impact of the contacts during closure. Contact impact generates vibration and results in a high level of noise.
Several structures have been designed incorporating an L-shaped armature and variations in contact orientation. Such structures improve upon the conventional relay by reducing the overall size of the relay and increasing operating efficiency. One such structure is described in U.S. Pat. No. 4,323,869 to Minks. This reference describes a relay having an L-shaped armature pivotally mounted on its vertex to a stationary yoke. A flat spring lies flat against a portion of the armature when the relay is in the normal state. When the coil in the relay is energized, the armature pivots to close the contacts. The flat spring presses against one edge portion of the armature exerting a small torque upon it. When the coil in the relay is de-energized, the spring torque forces the armature back into its original state. After repeated operation of this relay, however, the spring can become permanently deformed by the force exerted by the armature, resulting in a decrease in the reliability of the relay.
Another relay having an L-shaped armature structure is described in U.S. Pat. No. 5,070,315 to Kuzukawa et al. Like the Minks relay, the armature is pivotally supported at its inner vertex onto a yoke. A pair of contacts is spaced above one leg of the armature wherein the lower contact rests against the armature leg. When the coil is energized, the armature pivots so that the leg of the armature biases the lower contact upwardly to press against the upper contact. Careful positioning and spacing of the contacts relative to the armature is needed in this relay to ensure proper operation. Since both contacts are remote from the operating armature, complex additional structure is needed to secure the contacts in the relay, increasing material cost.
Another example of a relay having remotely located contacts which are indirectly actuated by a rockable L-shaped armature is shown in U.S. Pat. No. 4,020,434 issued to Jaegle et al. The shape and orientation of the armature in the relay forms two working air gaps. When flux is generated, the air gaps co-operate with permanent magnets to pivot and hold the armature in the desired position. One disadvantage of this approach is that permanent magnets increase the weight and cost of the relay.
A relay structure utilizing two L-shaped components is disclosed in applicant's Russian Inventor's Certificate SU1494019. A coil is mounted on a curved portion of an L-shaped core to generate an attractive force on a pivotable L-shaped armature. This structure enables flux lines to travel through both legs of the armature and create an attractive force between the core and the armature on each leg. However, the orientation and location of the coil on the core causes a decrease in the attractive forces when the vertex of the armature approaches juncture between the core and the coil, causing a decrease in the torque acting on the armature.